Although I don't have enough time to respond to all of your well written post, I do want to respond briefly to your last comment.

"Apart from having to ignore tonnes of ungrammatical expressions both in writing and when spoken, you have to speak SLOWLY and MORE CLEARLY... preferably as their Chinese teacher would - if she could speak ENglish at all." Linguisticus

I would suggest that your statement regarding the need of FT's to speak slowly and more clearly is in fact advice given to inexperienced teachers out of the need to provide them with a modicum of advise that they can carry with them to the classroom. Unfortunately, if after nearly two terms of teaching a particular class or classes, the FT is still speaking at the same pace as they were at the beginning - then they are actually supporting the notion that advancement is impossible. Experienced, well trained teachers on the other hand, know that they must challenge their students. I know that I needn't cite the relative research in this area to one who has the qualifications and experience that you possess; however, it must be noted that I+1 is relative to this discussion. We as teachers are as responsible for their advancement as the students are. Granted, there are mitigating factors, some of which you have addressed, that prevent us from following our own guidelines for excellence.

I do want to add, before rushing off, that, though this discussion, by virtue of the nature of forums, can't always deal with specifics, I think we need to avoid generalizations that reduce the validity of said discussion. There are always exceptions. I even see it in my classes as a whole. One class may be spot on, while another may drag me down into the doldrums they seem to get stuck in on any given day for no rhyme or reason. There are great classes and there are weak classes. There are great students and weak students. Some that care, some that don't. Some that are not the sons or daughters of the elite, some that are. And then there are those that fall into the middle of all these categories.